The long-term goal of this study is to understand the motor control processes underlying protective stepping for human balance recovery in older persons. Aging appears to present specific problems in controlling lateral stability. Impaired ability to generate rapid and controlled adductor-abductor muscular forces and postural movements may predispose many older persons to lateral instability and falls. This project focuses on the ways steps are generated to maintain balance under different directions of perturbed balance. Specifically, it will compare the ways younger individuals and active healthy community dwelling older persons control their body movements in response to different directions of postural disturbances. The authors propose that age-associated differences in frontal plane protective stepping patterns will indicate lateral instability in stance, and that these differences will be predictive of the risk of falling. This lateral instability may be associated with a reduced capacity to produce effective hip joint abductor-adductor torque-time responses to control frontal plane body motion and stepping. This may be reflected in impaired neuromuscular activation processes and/or in intrinsic changes in muscle contraction mechanisms. Identifying key motor control processes underlying protective stepping behavior as a function of age and future risk of falls will improve our understanding of the pathogenesis of disablement.